1. Field of the Invention
The present invention generally relates to discrete track recording methods, storage apparatuses and methods of producing storage apparatuses, and more particularly to a discrete track recording method for recording information on a magnetic recording medium having discrete tracks, a storage apparatus which employs such a discrete track recording method, and a method of producing such a storage apparatus.
2. Description of the Related Art
In storage apparatuses such as magnetic disk apparatuses (hereinafter simply referred to as magnetic disk drives), there are demands to improve the recording density of a magnetic disk and to realize an apparatus having a large storage capacity. The magnetic recording system employed in such storage apparatuses include the longitudinal magnetic recording system and the perpendicular magnetic recording system.
In order to improve the recording density on the magnetic disk, it is necessary to increase the track density. However, when the track density is increased to a high value, the writing that spreads at the time of the recording may affect an adjacent track and generate the so-called cross writing. When the cross writing occurs, a partial overwrite may be made with respect to information that is already recorded on the adjacent track, for example, and it becomes impossible in this case to guarantee a normal recording of the information.
On the other hand, in order to increase the track density to the high value, it is necessary to produce a recording head having an extremely narrow core width. However, when the core width of the recording head is extremely narrow, the inconsistencies in the core widths of the individual recording heads, generated due to inconsistencies introduced during the production process, become notable relatively. For example, even in the case of a magnetic disk that can realize a storage capacity SCA by using a recording head with a core width CWA, it is only possible to realize a storage capacity SCB (<SCA) by using a recording head with a core width CWB (>CWA).
Accordingly, if the designed value of the core width of the recording heads to be produced is CW but the recording heads that are actually produced have the core widths CWA and CWB due to the inconsistencies introduced during the production process, the storage capacity of the magnetic disk drive becomes different even when the same magnetic disk is used depending on the core width CWA or CWB of the recording head that is combined with the magnetic disk. In addition, if the actual core width of the recording head is considerably wider than the designed value, the effects of the cross writing become particularly notable.
For example, a Japanese Laid-Open Patent Application No.2006-31756 proposes a magnetic disk having discrete tracks in order to prevent the cross writing. Since a groove is provided between two mutually adjacent discrete tracks on the magnetic disk, it is possible to suppress the generation of the cross writing.
In order to further improve the track density of the magnetic disk having the discrete tracks, it is necessary to further reduce the core width of the recording head to a narrow value. However, as the core width becomes narrower, the inconsistencies introduced during the production process become more notable relatively. Further, because a track pitch of the magnetic disk having the discrete tracks is prescribed by separating the discrete tracks on which the information is recorded by the groove, the writing that spreads may reach the adjacent track and generate the cross writing if the core width is even wider than a predetermined core width (tolerable maximum core width) which is wider than the designed value (that is, too wide), and the writing that spreads may appear within the recording track and make it impossible to record the information in a positively readable manner if the core width is even narrower than a predetermined core width (tolerable minimum core width) which is narrower than the designed value (that is, too narrow). Moreover, if an attempt is made to reduce the effects of the core widths that are inconsistent by increasing the groove width, the recording track width is reduced by a corresponding amount, and it becomes impossible to secure a sufficiently large recording region on the magnetic disk. Hence, unless the inconsistencies of the core width of the recording head, caused by the inconsistencies introduced during the production process, are suppressed, it is difficult to further improve the track density.
According to the conventional magnetic disk having the discrete tracks, the groove is provided in advance at a constant pitch, and thus, the tracks that are separated by the groove are also formed in advance at a constant pitch. The recording head is produced to have the core width which is the designed value matching the constant track pitch. However, the actual core width differs among the individual recording heads due to the inconsistencies introduced during the production process, and the recording heads that are actually produced include recording heads having a core width wider than the designed value and recording heads having a core width narrower than the designed value.
For this reason, the recording head having the core width that is wider than the tolerable maximum core width and the recording head having the core width that is narrower than the tolerable minimum core width cannot be mounted in the magnetic disk drive, thereby making the production yield of the magnetic disk drive low.
On the other hand, if an attempt is made to improve the production yield of the magnetic disk drive by increasing the value of the tolerable maximum core width so as to increase the range of the core width of the recording head that can be mounted in the magnetic disk drive, it becomes necessary to increase the track pitch, and the track density is consequently reduced.
Therefore, in the conventional magnetic disk having the discrete tracks, there was a problem in that it is impossible to simultaneously improve the production yield of the magnetic disk drive and improve the track density of the magnetic disk.